US2996125A - Implement mounting system - Google Patents

Description

Aug. 15, 1961 E. v. BUNTING IMPLEMENT MOUNTING SYSTEM 8 Sheets-Sheet 1 Filed May 6, 1957 INVENTOR. ERNEST V. BUNTING BY wmfgm,

ATTORNEYS Aug. 15, 1961 E. v'. BUNTING IMPLEMENT MOUNTING SYSTEM 8 Sheets-Sheet 2 Filed May 6, 1957 HM 5 BBQ? INVENTOR.

ERNEST V. BUNTING ATTORNEYS.

Aug. 15, 1961 E. v. BUNTING 2,996,125

IMPLEMENT MOUNTING SYSTEM Filed May 6, 1957 8 Sheets-Sheet 5 2 X9 3 INVENTOR.

ERNEST V. BUNTING ATTORNEYS.

Aug. 15, 1961 E. v. BUNTING 2,996,125

IMPLEMENT MOUNTING SYSTEM Filed May 6, 1957 8 Sheets-Sheet 4 Us. w e 7? 7? I 2 5? H W; H w

ZNVENTOR. 329 ERNEST v. BUNTING ATTORNEYS.

Aug. 15, 19(51 E. v. aurwme 2,995,125

1549mm? MOUNTING SYSTEM Filed May 6, 1957' 8 Sheets-Sheet 5 as T 89 1 so 1 v I w: w

m? fl INVENTUR.

ERNEST V. HUNTING me By AT'FGRNEYS.

5, 1961 E. v. BUNTING 2,996,125

IMPLEMENT MOUNTING SYSTEM Aug. 15, 1961 E. v. BUNTING IMPLEMENT MOUNTING SYSTEM 8 Sheets-Sheet 7 Filed May 6, 1957 IIIC Ll.

N R 3 g a: Na f a INVENTOR. ERNEST V. BUNTI NG ATTORNEYS.

Aug. 15, 1961 E. v. BUNTING 2,996,125

IMPLEMENT MOUNTING SYSTEM Filed Bay 6, 1957 8 Sheets-Sheet 8 o h N K2 INVENTOR. I ERNEST V. BUNTING BY M W W4W'fi ATTORNEYS.

United States Patent 2,996,125 IMPLEMENT MOUNTING SYSTEM Ernest V. Bunting, Detroit, Mich., assignor to Massey- Ferguson Inc., a corporation of Maryland Filed May 6, 1957, Ser. No. 657,255 16 Claims. (Cl. 172-9) This invention relates to tractors especially intended for farming purposes and more particularly to tractors embodying control systems for usefully integrating the operational characteristics of the tractor and an implement associated therewith. Illustrations of the general types of tractors to which the present invention pertains are the well known Ferguson tractors.

Todays tractors are expected to handle a great variety of implements which may be mounted, semi-mounted or pull-behind types. These implements vary greatly in weight, dimensions and ground-engaging characteristics, such as rate of soil penetration, depth of operation and resistance to movement in the soil. In most tractors having control systems by which an implement may be lowered to a selected ground working depth and by which the draft load of the implement is utilized to automatically actuate a hydraulic system, such variations in implements seriously affect the response of the control system, and hence the operation of the tractor and implement unit. For example, a very heavy implement may drop too rapidly or a light implement may drop too slowly. This may be complicated further by light implements which have a large soil resistance and heavy implements having only a small soil resistance. In addition, the dimensions of certain mounted implements may vary to such an extent that the geometry of the hitch mechanism connecting the implement to the tractor affects the location of the virtual or theoretical hitch point from which the implement is propelled through the ground.

Even if all such implement variables can be accommodated satisfactorily, variations of soil "characteristics in any given area of operation may cause automatic depth control of the implement resulting in over corrections or corrections that are not required. For example, if the soil characteristics are such that 'the resistance decreased for only a fraction of a second, the control system will compensate for the decrease in draft by lowering the implement to a greater depth. However, by the time the correction is accomplished the soil characteristic may have returned to normal and another correction is re- .quired because the implement will then be operating at .an excessive depth. Consequently, it is important that instantaneous forces be distinguished from forces that change to and remain at some new value for a substantial period of time.

It is a general object of the invention to provide a new and improved hitch and control system for a farm tractor which is capable of accommodating a wide range (of implements varying in weight, dimensions and draft load and of controlling the operation of such implements in substantially the same manner and degree of effec- 'tiveness.

- It is another object of the invention to provide in a farm tractor a new and improved hitch and control sysfrom which is efiective to operate ground working or other implements either mounted on or pulled by the tractor.

A further object of the invention is to provide an improved control system of this nature by which the maximum rate at which the elevation of an implement will be decreased may be selectively varied to accommodate a wide range of implements in a manner making their operating characteristics similar.

It is also an object of the invention to provide a hitch and control system for a tractor implement operating unit which is capable of distinguishing between instantaneous forces imposed on an implement and those which persist for a substantial period of time, and of utilizing the persisting forces automatically to actuate means for chang-' ing the elevation of the implement.

A still further object of the invention is to provide a control system of this nature in which it is possible to select both the maximum rate at which an implement will be lowered and the interval of time required for the implement to achieve such a maximum rate of lowering.

Another object of the invention is to provide a mounting and control system which not only accommodates pull type implements but makes it possible to adjust hitch linkages associated with mounted implements to accommodate various implement dimensions and with any given implement to vary the geometry of such linkage to provide a hitch point on the tractor which properly meets the requirements of a given condition of operation.

It is still another object of the invention to provide a hydraulic control system by which a source of pressure fluid may in a new and useful way be made instantaneously available for the operation of auxiliary hydraulic systems.

The foregoing and other objects and advantages are attained by the present invention, various novel features of which will be apparent from the following description and from the accompanying drawings disclosing a preferred embodiment of the invention.

In the drawings:

FIG. 1 is a side view of a tractor and mounted implement incorporating the invention and shown with one of the rear wheels removed and with parts of the implement broken away for purposes of disclosure;

FIG. 2 is an enlarged sectional view of a rear portion of the tractor shown in FIG. 1;

FIG. 3 is a' perspective view diagrammatically showing internal and external portions of the mounting and control system incorporated in the tractor;

FIG. 4 is an enlarged sectional view with portions broken away and removed, and taken on line 4-4 in FIG. 2;

FIG. 5 is a further enlarged sectional view of a portion of the structure shown in FIG. 4 and taken from line 5-5 in that figure;

FIG. 6 is a partial sectional view of the control valve mechanism as shown in FIG. 2 and drawn at an enlarged scale;

FIG. 7 is an enlarged sectional view taken on 7--7 in FIG. 2;

FIG. 8 is an enlarged view of one portion of the control linkage shown in FIG. 2;

FIG. 9 is a view similar to FIG. 8 showing another position of the control linkage; and

FIG. 10 is a diagrammatic illustration of the modification of the hitch and control system used to accommodate pulled implements instead of the mounted implements shown in FIG. 1.

The tractor and implement hitch A preferred embodiment of the invention is incorporated in a tractor 11 having a rear housing 12 which, together with the engine 13 and the transmission housing 14, forms a frameless body supported on pneumatically tired traction wheels 16 and on front dirigible wheels 17. Although the tractor and its associated mechanism is adapted for use with mounted, pulled and other types of implements, reference will be made first to mounted im-Q plements and to the mechanism for operating them. Later reference will be made to the operation of other types of implements.

The tractor 11 is equipped with a three-point impleline absence ment hitch including upper link means in the form of a link 18 and lower link means formed by a pair of draft links 19 arranged in trailing relation to the tractor. The upper link 18 is pivotally connected by a pin to any one of a plurality of vertically spaced openings 20 in a bracket 21 formed integrally with the rear central portion of the tractor body and the lower links 19 are connected for universalswinging movement at opposite sides of a longitudinally movable control frame 22 supported. adjacent a lower side of the tractor body. The rear end of the upper link 18 is adapted for detachable connection to an upper point on an implement 23 shown partially in FIG. 1, by means of a pin 24 and the rear ends of the links 19 are provided with swivelly mounted balls 26 detachably receiving laterally spaced pins 27 on the implement and there is a comparable swivel connection between the implement and the upper link.

Referring to FIG. 4, the control frame 22 disposed adjacent the lower side of the tractor body is generally A- shaped and has forwardly converging side portions 31 and a transverse rearward portion 32 formed integrally with each other. The frame member is supported at its forward end by a bracket assembly 33 which, as shown in FIG. 5, includes a pair of vertically spaced plates 34 rigidly connected to the tractor by means of studs 36 threaded into the tractor housing 12. A roller 37 mounted between the plates for free rotation about a vertical axis is disposed in position to receive a slot 38 formed in the forward end of the frame member. The plates 34 support the forward end of the frame in vertically fixed relation relative to the tractor to permit'horizontal sliding movement of the roller 37 coacts with the slot 38 to guide the forward end of the frame member-in a fore and aft or longitudinal direction.

As best seen in FIGS. 2 and 4, the rearward end of the frame is suspended from the tractor by a pair of link assemblies 41 pivoted to and depending from opposite sides of the tractor body. The lower' ends of the links are pivotally connected to opposite sides of the frame 22 to swing about bolts 42 which also hold the balls 43 swivelly mounted in the forward 'ends' of the draft links 19. A support assembly 44'incl'uding a support member 45 disposed between the frame side portions 31, a bracket 46 disposed rearwardly of the transverse frame portion 32 and a plate 47 passing under the frame 22 are all held rigidly relative to each other 'and'to the tractor by studs 48 threaded into the tractor housing '12. A roller 49 (FIG. 4) is supported between the plate '47 and the bottom of the housing 12 for rotation on a vertical axis and in position to receive a slot 50 formed in the transverse portion 32 of the frame member. The forwardly located bracket assembly 33 and the rearwardly located links 41 permit substantially horizontal fore and aft movement of the frame member 22 with the rollers 37 and 49 preventing lateral displacement thereof relative to the tractor.

Longitudinal movement of the frame member 22 is resisted by a spring 53 which has its opposite ends fitted with identical caps 54 and 55. The forward end of the frame 22 is provided with an element having a conical head 56 which fits into a complementary opening in the spring cap 54 and the rearward end of the frame rigidly mounts a plunger element 57 having a conical head 58 received in a complementary seat in cap 55. The plunger element is threaded into the transverse frame portion 32 and is free to slide through a collar 59 threaded into the support member 45. Thus, spring53 is held relative to the frame 22 by the seated conical heads 56 and 58 with the cap 54 abutting plates 34 and cap '55 abutting the end of the collar 59. With this arrangement forward movement of the frame '22 is resisted by the spring 53 reacting between the plunger head 58 and the plates 34 and rearward movement of the frame is resisted by the spring reacting between the seat element 56 and the collar 59. The collar may bescrewed' relative to" the 4 support member 45 and the plunger 57 may be screwed relative to the frame 22 to adjustably select the initial load on the spring 53 which must be overcome to move the frame 22.

Fore and aft movement of the frame against the resistance of spring '53 -is brought about by ground loads imposed on the implement 23, which tilt the implement about the upper pin 24 shown in FIG. 1 and move the frame through draft links 19. Such movement of the frame is used to automatically actuate a hydraulic control system incorporated in the tractor to bring about corrective positioning or elevation of the three-point hitch and its associated implement. Actuation of the system may also be accomplished manually by proper manipulation of a hand control arrangement including levers 61 and 62 disposed within convenient reach of the operators seat 63.

Hydraulic power mechanism In the preferred embodiment of the invention, raising and lowering of the draft links 19 is accomplished by means of a hydraulic system which, as shown in FIGS. 2 and 3, includes a pump 66 immersed in a fluid reservoir 67 formed by the walls of the tractor housing 12. The pump is driven by the tractor engine 13 and is capable of delivering hydraulic fiuidfrom the reservoir 67 surrounding the pump to a hydraulic actuator 68. The illustrated actuator is a one-way ram comprising a cylinder portion 69 formed integrally with and at the interior of a cover housing 71 mounted on the top of the housing 12. The cylinder opens to the rear and slidably receives a piston 72 having a connecting rod 73 projecting rearwardly. The rearward end of the rod is ball shaped and is received in a socketed lower end of an arm 74 rigidly connected to a transverse rock or lift-shaft 76 having its intermediate portions journaled in the cover housing 71. Each end of the lift shaft 76 has a crank arm assembly 77 having a crank arm 77a splined on the shaft and connected to one of the lower draft links 19 by a drop link 78. The arrangement is such that when pressure fluid is supplied to the closed end of the cylinder 69, the piston rod 73'is forced rearwardly and the arm 77 swings upwardly to raise the lowered draft links 19. In like manner, when fluid is exhausted from the cylinder the piston 72 retracts due to the weight of the links and implement so that the links 10 swing downwardly. Furthermore, when the implement is in a ground working position, fluid may be maintained in the cylinder so that the implement is literally supported on the oil and the load of the implement is added to that of the tractor to increase traction.

The volumetric rate at which oil is supplied to or exhausted from the cylinder 69 determines the rate at which the draft links 19 and the implement thereon are either raised or lowered. In the present system, oil is supplied from the pump 66 driven continuously by the engine and since the engine speed necessarily varies to meet the various demands made on the tractor, the volumetric delivery rate of oil is controlled by varying the amount of oil permitted to enter the pump. Such control is obtained through a valve 80 which also controls the rate at which fluid can escape from the ram or motor 68.

Control valve mechanism The function of the control valve 80 is to prevent the flow of fluid or to meter fluid to or from the pump. The valve mechanism is immersed in fluid in the reservoir 67 and is located in a housing 81 at one side of the pump 66. As shown in FIG. 6, the valve includes a generally tubular valve means or plunger 82 supported for axial movement in spaced rings 83, 84 and 85 mounted in a bore 86. Rings 83 and 84 are held in spaced relation by a sleeve 87 to form a chamber 88 which communicates with a 1 pump discharge passage 89 through large ports 90 formed which communicates through ports 95 with a pump intake passage 96.

' When the valve plunger 82 is in its neutral position, as shown in FIG. 6, the outer surface of the plunger 82 bridges the rings 83, 84 and 85 so that the flow of fluid in the passages 89 and 96 is prevented and fluid is locked in the system.

As the valve plunger 82 is moved axially and downwardly from its neutral position shown in FIG. 6, a pair of narrow axially extending slots 98 and a pair of wider and shorter slots 98a in the end of the plunger move past the ring 83 and permit fluid to escape from the pump 66, through the passage 89, chamber 88, the interior of the plunger 82 and through the open end 99 of the stepped bore 86 to the reservoir. This also exhausts fluid from the cylinder 69, allows the piston rod 73 to retract into the cylinder and the links 19 to swing downwardly.

' The maximum rate of lowering of the implement hitch linkage depends on the rate at which fluid can escape from the system. This in turn is dependent on the effective area of the escape or drop ports formed by slots 98 and 98a which are exposed to the chamber 88. The effective length of the slots increases progressively as the plunger 82 is moved downwardly from a neutral position and the volume of escaping oil also increases progressively so that the implement will drop at an increasing rate until the effective area of the slots 98 and 98a reaches a maximum.

- As the plunger 82 moves in the opposite direction or upwardly from a neutral position, the chamber 88 remains closed by the outer surface of the plunger and a pair of large slots 181 (only one of which is shown) at the lower end of the plunger pass upwardly through the ring 85 and enter the chamber 94. Oil in the reservoir is free to enter open cap 102 bolted to the bottom of the valve housing and toflow through the slots 101 into the low pressure chamber 94 and then through the large ports 95 in the sleeve 93 to the intake passage 96 of the pump. Oil is then forced by the pump to the hydraulic actuator 68 causing the piston rod 73 to extend and to swing the arms 77 upwardly for raising the hitch linkage and implement.

Mechanism for moving the valve plunger 82 includes a plunger rod 103 which is held in abutment with one side of an internal flange 104 in the plunger 82 by means of a screw 105 in the end of the rod 103 and a spring 106 which acts between the head of the screw and the other side of the flange. The upper end of the rod 103 projects into a cylindrical housing 107 supported at the top of the valve housing 81 and is provided with a connector 108 for receiving the spherical end 109 of a rod 111 projecting through the upper end of the housing 107. A spring 112 is mounted on the rod 111 and within the housing 107 to react between the connector 108 and the upper end of the housing. The spring is effective to urge the rods 111 and 103 downwardly to move the valve plunger 82 toward its discharge position. The upper end of the rod 111 is pivotally connected at 114 to one end of an arm 113, which as shown in FIGS. 2 and 3 has its other end connected to additional valve actuating mechanism.

Valve actuating mechanism The mechanism for actuating the valve affords both movement of the valve plunger 82 and the implement is raised to reduce the implement load or is lowered to increase the load so that the frame will return to its original position and permit the valve plunger 82 to return to its neutral position. This type of control makes it possible to maintain a substantially constant load on the im- ;plement and is referred to as draft control. The lever 62 may be termed a draft control lever and is used to ad-I just the relationship between the frame 22 and the valve plunger 82 to determine the implement load which in operation is required to automatically maintain the valve plunger at its neutral position. The other lever 61 is used to raise and lower the implement between transport and ground working positions at which the implement becomes subjected to draft control. The operation obtained with lever 61 may be termed position control since move ment of the lever from one end of its range to the other causes a corresponding movement of the hitch linkage throughout its entire range.

Position control Referring now to FIGS. 3, 8 and 9, the position control lever 61 extends radially from one end of a hollow shaft 116 journaled in the side of the housing and has its other end disposed within the housing. The end opposite the lever is provided with a circular cam 117 mounted eccentrically of the shaft and positioned between a pair of jaws 118 and 119 formed on the end of a cam lever 121. The cam lever is mounted to pivot about a pin 122 between the side elements 123 of a double link assembly 124 and the forward end is pivotally connected by a pin 126 to a depending link 127 having a slot 128 in its lower end to receive a pin 129 in the rearward end of the rocker arm 113. If the pivot pin 122 is held stationary, rearward movement of the position control lever 61 from the position shown in FIG. 3 forces the circular cam !117 against the jaw 118 to move the cam lever in a clockwise direction about the pin 122. The forward end of the lever 121 and the link 127 will swing downwardly so that the upper end of the slot 128 acts against the pin 129 on the rocker arm 113 to swing the latter in a counterclockwise direction about its pivot pin 131. Such movement is effective to move the valve plunger 82 upwardly to an intake or supply position which results in admission of fluid through the passage 96 to the pump and delivery from the pump through the conduit 132 to the actuator 68 for raising the hitch linkage.

Forward or clockwise movement of the lever 61 forces the circular cam 117 against the other jaw 119 to swing the forward end of the cam lever 121 upwardly together with the link 127. As the slot 128 in the link 127 moves upwardly and the spring 112 urges the valve plunger 82 downwardly from its neutral position and-at the same time swings the rocker arm 113 so that the pin 129 is maintained in engagement with the upper end of the slot 128. During downward movement of the plunger 82 fluid is discharged from the actuator 68 through conduit 132 and passage 89 to the reservoir.

As pointed out above, movement of the position control lever 61 in opposite directions from the position shown in FIG. 3 will cause movement of the valve plunger 82 from its neutral position to either a fluid supply or to a fluid discharge position. This brings about movement of the lift arms 77 which actuates a follow up mechanism for returning the valve plunger to neutral to stop further movement of the hitch linkage when it reaches a position corresponding to the location of the lever. This mechanism includes the double link assembly 124 which has a rod 136 mounted to slide through a spacer element 137 rigidly joining the ends of the side elements 123. The forward end of the rod mounts a slide element 138 which extends through aligned slots 139 in the side elements 123. A compression spring 141 surrounds the rod and reacts between the spacer 137 and slide element 138 to normally maintain the double link assembly in the condition shown in FIG. 8. The forward end of the link assembly 124 is pivotally connected to the cam lever 121 by the pin 122 and the rearward end of the rod is provided with a clevis 142 pivotally connected to a lever 143 by a pin 144. An intermediate portion of the lever 143 is supported on a pin 145 rigid with the cover housing 71 and the upper end of the level i is adapted to engage a stud 146 fixed to the actuating arm 74.

When the lift arms 77 are in a raised position and the control lever 61 is moved forwardly from the position shown in FIG. 3 to a new position, the cam lever 121 swings counterclockwise permitting movement of the valve plunger 82 to its discharge position to permit lowering of the implement hitch. As the hitch drops the lift shaft 76 rotates in a counterclockwise direction and the stud 146 swings the lever 143 clockwise to pull the link assembly 124 rearwardly. This swings the cam lever 121 clockwise about the circular cam 117 as a pivot and returns the valve plunger 82 to neutral as the implement hitch drops to an elevation corresponding to the location of the position control lever.

When the lift arms 77 are in a lowered position, as shown in FIG. 9, rearward movement of the position control lever 61 will swing the end of the cam lever 121 downwardly and move the valve plunger 82 (FIG. 3) upwardly from its neutral position to an intake position. This brings about a delivery of fluid to the actuator 68 which causes upward swinging movement of the lift arm 77 and rearward swinging of the actuator arm 74. As the stud 146 retreats rearwardly the lever 143 remains in engagement with the stud due to the movement of the link 124, cam lever 121, link 127 and rocker arm 113, which is caused by thespring 112 associated with the valve plunger 82. The valve plunger 82 remains in an intake or supply position as long as the position control lever 61 is being moved rearwardly. However, when movement of the lever 61 stops, the rearward moving stud 146 and the follow-up mechanism permits the spring 112 to return the valve plunger 82 from an intake position to its neutral position. As the valve plunger 82 reaches its neutral position, movement of the lift mechanism, including the arms 77 and 74, stops and all the movable mechanism is stationary.

If the lever 61 is moved slowly from the position shown in FIG. 9, the lift arms 77 will swing upwardly to positions which at any given time will correspond to the position of the lever 61. When movement of the lever 61 stops the lift arms 77 will also stop and the hitch linkage will remain at an elevation which corresponds to a given position of the control lever 61. However, if the position control lever 61 is jerked rearwardly and upwardly, it may be possible to achieve a condition in which hydraulic fluid cannot be supplied to the actuator fast enough to swing the lift arm 77 upwardly and actuate the follow-up mechanism. Under this condition the follow-up mechanism will remain momentarily stationary and the cam lever 121. will swing about its pivot 122 so that the lower end of the lever 127 moves downwardly into engagement with an internal wall 150 of the housing 12 as best shown in FIG. 2. Thereafter, the rotating cam 117 will force the cam lever 121 forwardly and will extend the link 124 against the action of spring 141. As soon as suflicient fluid reaches the actuator 68 so that the lift arms 77 will move upwardly, the lever 143 is free to follow the movement of the stud 146 and the spring 141 collapses the link 124 to its original position. In this manner the extensible link 124 forms a breakout mechanism which protects the various internal control linkages when the position, control lever 61 is moved so rapidly that the hydraulic system and the follow-up mechanism cannot immediately respond.

The position control arrangement just described makes the plunger 82 responsive to movement of both the lever 61 and links 19 to bring about movement of the latter to an elevation corresponding to the position of the lever.

Draft control The draft control lever 62 shown in FIG. 3 extends radially from one end of a shaft 151 supported in the hollow position control shaft 116. The other end of the shaft is provided with a circular cam 152 mounted eccentrically of the shaft and disposed between jaws 153 and 154 of a cam lever 156. The earn lever is pivotally connected to a link 157 which is also pivoted on. the pin 129 at the end of the rocker arm 113. Thus far the draft control mechanism is very similar to the position control mechanism and movement of the lever 62 in a clockwise direction from the position shown in the drawings is effective to bring about movement of the cam lever 156 similar to the movement of the cam lever 121 associated with control. lever 61.

Movement of the cam lever 156 may also be effected by movement of the control frame 22 at the bottom of the tractor. The mechanism for accomplishing such operation includes a shaft 161 journaled for rotation in the side of the housing 12. As seen in FIG. 3, the inner end of the shaft rigidly supports a pair of aligned, radially extending arms 162 which are pivotally connected at opposite sides of the cam lever 156 by a pin 163. The other end of the shaft which is disposed externally of the housing is provided with a crank arm 164 having its free end pivotally connected to a clevis 165 at the end of a rod 166. The rod 166 is telescoped into a tubular link 167 having its lower end pivotally connected to an arm 168 of a bell crank 169 pivotally mounted on the exterior of the tractor housing 12. The other arm 178 of the bell crank is maintained in engagement with a stop 171 formed integrally with the control frame 22 by means of a tension spring 172 acting between the arm 168 and a point on the tractor body. The spring also urges the upper end of the tubular link upwardly into engagement with the nuts 174 on the rod 166. Engagement of the link 167 with the nuts 174 affords a one-way connection between the frame 22 and cam lever 156 which may be adjusted by moving the nuts axially of the rod 166.

During ordinary operation with the implement in the ground, the draft control lever is maintained at a point forwardly or clockwise of the position shown in FIGS. 2 and 3. This point will correspond to a position of the frame and a deflection of the spring 53 which will maintain the valve plunger 82 at neutral. Any variation in the reaction on the implement sufficient to cause a deflection of the spring and a change in the position of the control frame 22 will cause movement of the bell crank 169 and arm 164 to pivot the cam lever 156 about the circular cam 152 and bring about movement of the valve plunger 82 from a neutral position. The accompanying change in elevation of the hitch and implement will vary the reaction on the implement so that the spring 53 will return the control frame 22 to its nor-. mal position and effect a return of the valve to neutral. If the operator desires to operate the implement at a deeper position in the ground, he may move the lever 62 forwardly. This lowers the implement and as the load on the implement increases and deflects the spring to some new value, the plunger returns to neutral. Consequently, the lever 62 may be considered as a means for selecting various values of spring deflection and, consequently, positions of the control frame 22 at which the valve plunger 82 will be maintained at neutral.

Relation of draft control and position control Thus far the operations of the position control and draft control systems and their eifect on the valve plunger 82 have been considered independently of each other. The relation of the two systems and their effect on each other will be more readily understood by consider ing a complete lifting and lowering cycle of the implement hitch linkage.

If the initial condition is as shown in FIG. 3, the hitch linkage will be raised and the implement will be at its transport position. When the draft control lever 62 is moved forwardly to the lower end of its range, the forward end of the cam lever 156 ordinarily would swing upwardly. However, the link 127 associated with the position control system is held against movement so that the pin 129 at the end of the rocker arm 113 is stationary. Because of this, clockwise movement of the draft lever 62 does not move the valve plunger 82 and cam lever 156 instead moves rearwardly and results in counterclockwise movement of the arms 162 and 164. This slides the rod 166 upwardly in tubular link 167 which is held against movement by the bell crank 169 and control frame 22. Subsequent clockwise movement of the position control lever 61 toward the lower end of its range will swing the end of the cam lever 121 and its associated link 127 upwardly. As the slot 128 moves upwardly, the valve spring 112 moves the valve plunger 82 downwardly from its neutral position to its discharge position to lower the implement. While this is occurring the pin 129 is maintained in engagement with the upper end of the slot 128 in the upwardly moving link 127. The pin 129 will also be effective to swing the draft control cam lever 156 about the pivot afforded by cam 152 so that arms 162 and 154 rotate in a clockwise direction permitting rod 166 to telescope into link 167. The hitch linkage and implement will continue to drop until the follow up mechanism including the lever 143 and the link assembly 124 returns the valve to neutral to stop further movement of the hitch linkage.

If the position control lever 61 is moved downwardly to the end of its range the mechanism associated with the position control system will be ineffective to return the valve plunger 82 to neutral since the draft control linkage including the cam lever 156 will be held stationary by the frame 22. This will maintain the valve plunger 82 in its exhaust position and the implement will continue to drop until the valve plunger is returned to neutral by some other means. As previously pointed out, the draft control lever 62 and the associated linkage makes it possible to select a position of the control frame 22 which is effective to maintain the valve plunger at its neutral position. Consequently, when the valve plunger is in its exhaust position and the implement drops in the ground, a load is imposed on the implement which moves the control frame rearwardly. After the load increases sufliciently, the frame will reach a position which corresponds to a neutral position of the valve and further flow of hydraulic fluid will be blocked. Under these conditions the implement is subjected to automatic draft regulation and any change in load on the implement will cause a corresponding change of position in the control frame 22 which in turn effects a change in elevation of the implement. The implement will move towards its new elevation until the load reaches a value required to maintain the frame at its original position. If the depth at which the implement is operating is not satisfactory the operator may move the draft control lever 62 a slight amount to select some other depth of operation and a load which will maintain the valve plunger at its neutral position.

.To raise the implement, the operator moves only the position control lever 61 in a counterclockwise direction. This forces the cam lever 121 downwardly and swings the rocker arm 113 counterclockwise to move the valve plunger toward an intake position so that oil enters the pump and is delivered through the conduit 132 to the actuator 68 for raising the implement. During this operation the rod 166 slides freely in the tubular link 167 so that there is no need to move the draft control lever 62 from its selected position and it may be left in readiness for operation when the implement is returned to the ground. It is, therefore, a lever settable to condition the system for response to a selected draft load.

Modifying the control system for different implements Because of the wide range of implement types used on tractors a change from one implement to the other requires variation in the response characteristics of the system in order to realize equally eflicient operation for all implements. For example, if the system is sensitive enough to respond satisfactorily for a light implement such as a cultivator it will over control and cause erratic performance when a heavy implement such as a four-bottom plow is attached to the hitch linkage. Conversely, if the system is adjusted for controlling a heavy implement, a light implement may be ineffective to bring about the necessary control action. Heavy implements which encounter light soil reaction and light implements which encounter large soil reaction further complicate this problem.

The problems relating to response characteristics may be readily appreciated by considering the implement and its hitch linkage as being supported on the tractor through means of the oil in the hydraulic actuator 68 so that the weight of the implement '23 is borne by the oil and, consequently, by the tractor. The rate at which oil is supplied to the actuator determines the rate of raising of the implement and the rate at which fluid is permitted to es cape determines the rate of lowering.

It has been found that the rate of exhaust of fluid from the actuator is critical with respect to the operating characteristics of the system. For example, if oil is dumped instantaneously from the actuator 68 it will no longer support the weight of the implement and the effective weight of the implement on the rear wheels of the tractor may be reduced so dastically that tractive effort decreases. In certain instances this may cause the tractor wheels to spin so that forward motion of the tractor and implement stops. For this reason implement drop must be slow enough in normal operation so that some of the implement load is maintained by the oil in the actuator even though the implement is being lowered. Also, when the implement is lowered from the transport position on the tractor, the rate of drop must be slow enough so that shock loads are not imposed on either the implement or the hitch linkage when the implement stops or reaches the ground.

To control the rate of drop the volumetric rate of oil discharge from the actuator must be subjected to control and in the present system this is accomplished through means of the valve plunger 82. The rate of oil discharge is dependent on the downward load on the implement such as the implement weight and ground load acting to force oil from the hydraulic actuator, the maximum size of the valve ports or vents 89 (FIG. 6) which becomes exposed to the chamber 88, and also on the length of time required for the valve plunger 82 to move from its closed or neutral position to an open or discharge position.

The maximum rate at which an implement will be raised is not so critical since the rate of implement movement is dependent on the volumetric displacement of the pump which, in turn, is dependent on the engine speed. Because of this the diiference in the rates at which heavy and light implements are raised is slight. Furthermore, no matter how rapidly an implement is raised there is no problem of losing the support of the oil in the cylinder and the implement weight will be maintained on the tractor throughout the raising cycle to aid tractive effort.

In the present system the rate of response is controlled by varying the maximum extent of movement of the valve plunger 82 and also by varying the time interval required for the valve plunger to move its full extent from a neutral position at which the rate of discharge is zero to a fully opened or discharge position at which the rate of discharge is at a maximum.

The extent of movement of the valve in the discharge direction is determined by an adjustable stop which, as seen in FIGS. 2 and 3, includes a cam 176 fixed on the end of a rotatable shaft 177 journaled in the wall of the housing 12. The cam 176 is engageable with the forward end of the position control cam lever 121 to limit its upward or counterclockwise movement and, consequently, the downward movement of the valve plunger toward discharge. The outer end of the shaft mounts a lever 178 which may be rotated in a clockwise direction from the position shown in FIG. 2 to increase the extent ofimovement ofthe. camlever 121 upwardly. As pre viously pointed out, the camlever 121 istconnected. to thecam lever 156. associated with the draft control lever 62; through link 127, pin 129 and a link 157. Because ofthis, the cam 176 and lever 178 are effective to determine the maximum extent of movement of the valve plunger 82 ina discharge direction when such movement is caused by either the draft or the position control systerms.

The time required for the valve plunger 82 to. move from neutral to its maximum discharge position as determined by the adjustable stop or cam 176 is under the influence of control. means in the form of a clamping device 180. As seen in FIGS. 2, 3 and 7, the damping device includes a body member 181 immersed in fluid in the reservoir 67 and attached to the side of the valve housing 81. The body member is provided with a bore forming a cylinder 182 sealed at its lower end by a plug 183. A piston element in the form of a washer 184 is slidably disposed inthe cylinder and. is biased upwardly by a spring 186 reacting against the plug 183. The piston 184 is moved against the action of the spring 186 by a control rod 187 slidably supported at its upper end by a bracket 183 attached to the tractor body 12. The lower end of the rod 187 is. slidably supported in a washer 189 seated in cylinder 182 on a snap ring 190 fitted into the wall of the cylinder. A collar 192 is attached adjacent an upper end of the rod 187 by a screw 193 to limit upward movement of the rod and to provide a seat for the upper end of a spring 194. The spring reacts against the collar 192 to maintain the washer 189 seated against the ring 190 and also to urge the rod upwardly to move the collar 192 into engagement with the bracket 188. The upper end of the rod 187 is adapted to engage the rocker arm 113 which has its forward end guided by a slot 195 in the bracket 188. When the valve plunger 82 is at neutral a head portion 196 at the end of the rod 187 is effective to close an opening 185 in the piston 184. During downward movement of valve plunger 82 from its neutral position the rocker arm 113 will swing counterclockwise and move the rod 187 and piston 184 against the action of spring 186. Upon counterclockwise movement of the rocker arm 113 the spring 194 maintains the rod in engagement with the arm 113 and the spring 186 moves the piston 184 upwardly to follow the movement of the rod 187.

The upper end of the cylinder 182 is in communication with the reservoir through means of a passage 197 and the lower end of the cylinder communicates with the passage 197 through a passage 198. The communication of the passage 197, 198 is controlled by a needle valve element 199 coacting with the seat 200 to form an adjustable orifice or port in the body member 181. The needle valve includes a vertically extending rod assembly 201 slidably supported in washer 202 at the top of the damping body 181 and in a flange 203 formed integrally with an internal wall of the rear housing 12. The rod assembly 201 is biased upwardly by a spring 204 reacting against the washer 202 and a collar 206 fixed on the rod 201. The upper end of the rod is engaged by a cam 207 rotatably supported in the wall of the housing 12 by a shaft 208. The end of the shaft 208 at the outside of the housing is provided with a lever 209 by which the cam 207 may be rotated to force the rod 201 downwardly against the action of spring 204 to determine the position of the needle valve 199 relative to its seat 200.

When spring 112 moves the valve plunger 82 toward discharge the accompanying movement of the rocker arm 113 is effective to move the rod 187 and the piston 184 downwardly to force oil out of the lower portion of the cylinder 182 and into the passages 198 and 197. At the same time, oil is drawn into the upper end of the cylinder 182 through the passage 197. Adjustment of the opening by means of needle valve 199 varies the rate at which oil will be forced from the cylinder 182 by virtue of, the spring 112 acting through rocker arm 113 androd 187on the piston 184. Since the plunger 82 moves:

from, neutral to discharge together with the piston, the rate of plunger movement, can also be varied.

To. return the valve plunger 82 to its neutral position by means of the draft or position control mechanisms, it is necessary to force the arm 113 in a counterclockwise direction to overcome the force of the spring 112. When this occurs the spring 194 moves the rod 187 upwardly and keepsit in constant engagement with the end of the rocker arm 113. This will uncover the opening in the piston 134 and as the piston is urged upwardly by the spring 186, oil will pass from the upper part of the cylinder through the opening 185 to recharge the lower end of the cylinder.

Although the piston 184 is effective to retard the rate of valve plunger movement from neutral to a discharge position, the valve plunger is free to move in a return direction independently of the damping piston because of. the one-way connection between the lower end of the rod 187 and the piston 184. Movement of the valve plunger 82 between its neutral and intake or implement lift position is also accomplished independently of the damping device since the collar 192 engages the bracket 188 (FIG. 7) when the valve plunger is at neutral. Thereafter the right end of the rocker arm 113 moves upwardly, free of the rod 187.

As pointed out previously, the cam 176 associated with thecam. lever 121 is effective to limit the extent of movement of the valve plunger 82 downwardly in an implement lowering direction. Since such movement progressively opens slots 98 in the valve plunger 82, the volumetric rate of fiuid discharge from the actuator 68 and consequently the rate of implement descent will be increased progressively until the valve plunger reaches its maximum extent of movement. Thereafter, the rate of implement drop will be constant until the implement reaches its lowest possible position. The cam 176 is effective to adjust the system to accommodate various weights ofv implements. For example, a light implement may require a large maximum opening and a heavy implement may require a small maximum opening in order to obtain the same desirable rate of implement descent. The rate of descent may be further controlled by the damping mechanism which can be adjusted through the valve 199 to vary the rate of valve movement over its full extent of movement from neutral to discharge.

The damping device is of particular utility in avoiding overcorrections during automatic draft control since it is capable of determining the permanence of a force applied to the implement. For example, when an implement is operated in caked soil which imposes a large load on the implement, a sudden shattering of the soil reduces the load substantially but almost instantly the load will return to its normal value. Such a reduction in load will cause the control frame 22 to move forwardly and the valve plunger 82 would ordinarily move in a discharge direction and lower the implement. When the load increases to normal, the implement would be operating at too great a depth and another correction would normally be required to raise the implement to its original depth of operation. By using the damping mechanism, the cylinder 182 retards the rate of movement of the plunger 82 so that it does not have enough time to move to an implement lowering position before the control frame 22, and the various plunger actuating mechanisms, returns to its normal position. In this manner an instantaneous reduction in force becomes ineffective to bring about corrective movement of the implement. If, however, the load decreases and remains at some new value, the valve plunger 82 can move in a discharge direction at a retarded rate.

Control of mounted implements is also affected by the location of the point from which the implement is pulled. By utilizing a hitch having upper and lower link means 18 and 19 converging forwardly relative to each other the point of convergence acts as the hitch point for the implement. It is possible to locate the point of convergence or virtual hitch point forwardly on the tractor at a location normally not available for hitching an implement. As an example, the virtual hitch point for the arrangement shown in FIG. 1 is indicated at X. Because implements vary in size, the vertical spacing between the pins 24 and 27 may vary and change the geometry of the hitch linkage to such an extent that the virtual hitch point changes to some undesirable location. This difficulty is avoided through means of the bracket 21 which affords vertical adjustment of the forward end of link 18. In FIG. 1, the point of convergence of link 18 and draft links 19 is at X. With an implement other than the one shown in FIG. 1, the spacing between the pins 24 and 27 might increase and move the virtual hitch point rearwardly. The point could be relocated forwardly near its original location by adjusting the forward end of the link 18 vertically to a higher position on the tractor.

Adjustment of the upper link 18' is also important for changing the location of the virtual hitch point to meet the demands of certain types of operating conditions. During operation of an implement in the ground, it is desirable to maintain the virtual hitch point at a constant elevation above the ground so that the attitude or angle of the implement relative to the ground does not vary. Such a change in angle will affect the tendency of the implement to go deeper or shallower in the ground. If the virtual hitch point is located at the point Y in FIG. 1 and the front wheels 17 drop into a ditch, the virtual hitch point also drops and the implement angle changes with relation to the surface of the soil in the area of the implement. However, if the virtual hitch point is located at Z or close to the rear axle of the tractor, the virtual hitch point will remain at substantially the same level-even though the front of the tractor has moved vertically. In like manner, when an implement is operated in soil of varying compactness, the drive wheels 16 of the tractor are apt to spin and tend to dig deeper. Also, the soil variations will cause corrections by the automatic draft control system and bring about periodic tire deflection causing vertical movement of the rear portion of the tractor. In such instances, it is desirable to locate the virtual hitch point forwardly on the tractor as at Y. In this manner, the virtual hitch point will be maintained at a substantially constant elevation even though the rear portion of the tractor moves. To accommodate these conditions with the implement shown in FIG. 1, it is merely necessary to adjust the forward end of the top link 18 to a new position on bracket 21 to select the location for the virtual hitch point.

The converging upper and lower link means 18 and 19 afford a virtual hitch point forwardly of the points to which the link means are connected to the tractor. This hitch point remains at a substantially constant elevation above the ground during fore and aft movement of the control frame 22. However, when such frame movement brings about changes in the implement elevation, the virtual hitch point also changes and affects the attitude of the implement. For example, when an implement is lowered the virtual hitch point shown at X will move upwardly and forwardly and because of the difference in lengths of the links 18 and 19, the implement will tend to tilt rearwardly thereby decreasing its angle of attack to the soil. As previously pointed out, it is important to lower the implement at a rate slow enough to maintain a load on the tractor. It will also be appreciated that the position of the virtual hitch point must change slowly so that the angle of attack of the implement is not changed abruptly. Since the damping device 180 retards the rate of movement of the valve means or plunger 82 in a discharge direction to some selected rate, it is also effective to control the rate at which the virtual hitch point changes position to affect the attitude of the implement.

Operation 0 pulled implements Thus, far, the implement hitch and control system has been described in terms of implements mounted integrally with the tractor. However, the wide range of implements in use also requires that a tractor be adapted for pulling and controlling self support implements. The present invention makes it possible to accomplish both automatic draft control and position control even through the implement is not supported on the tractor.

In FIG. 10 an implement 215 diagrammatically represents most pulled implement types which include a frame 216 and a ground engaging tool 217. The forward end of the frame is connected to the control member 22 on the tractor and the rearward part of the frame 216 is supported relative to the ground by a swinging wheel assembly 218 pivoted at 219. An auxiliary actuator 221, including a double ended cylinder 222 is mounted on the frame and is provided with a piston 223 having a rod 224 connected to the wheel assembly 218. The auxiliary actuator 221 is placed in fluid communication with the tractor hydraulic system by a pair of conduits 226 and 227 connected to opposite ends of the cylinder 222 and to spaced points in the conduit 132 which extends from the pump 66 to the actuator 68. A shutoff valve 228 is placed in the conduit 132 between the conduits 226 and 227 to prevent flow of fluid from the pump directly to the actuator 68. In the preferred embodiment of the invention, the shutoff valve 228 and connecting points for the conduits 226 and 227 may be incorporated in a plate 229 interchangeable with a block or transfer plate 230 which, as shown in FIGS. 2 and 8, is bolted to the top of the cover housing 71. The plate actually forms a part of the passage 132 to the actuator. Consequently, substitution of the plate 229 for the transfer plate 236 affords external connections for the conduits 226 and 227 and the shutoff valve 228 therebetween.

Automatic draft control of a pulled implement 215 is similar to that for a mounted implement 23 and an increased load on the tool 217 causes rearward movement of the frame 22 and movement of the control plunger 82 to permit delivery of pressure fluid through the conduit 132. Because the shutoff valve 228 blocks flow of fluid to the actuator 68, it is delivered through the conduit 226 to one side of the piston 223 and causes raising movement of the implement frame 216. As the imple ment raises it brings about a reduction in load and the frame 22 is returned to its normal position by the spring 53. This returns the valve to neutral and prevents further fluid delivery. On the other hand, when the load on the tool 217 decreases the frame moves forwardly and the valve plunger 82 moves to an exhaust position permitting the weight of the implement 215 to collapse the auxiliary actuator 221 and force fluid to return to the reservoir through the conduit 226.

The modified system shown in FIG. 10 also makes it possible to move the implement to an elevation corresponding to that of the position control lever 61. In the case of mounted implements, movement of the lever 61 shifts the valve plunger 82 fromits neutral position to bring about a flow of fluid in the system. When the lever movement stops, it is necessary to actuate the follow up linkage including the lever 43 and the link 124 shown in FIG. 8, to return the valve plunger 82 to neutral and prevent further fluid flow. The follow up mechanism is activated by movement of the shaft 76 and the arm 74' associated with the hydraulic actuator 68. In the case of the pulled implement 215 shown in FIG. 10, movement of the lever 61 to a rearward position causes delivery of fluid to the auxiliary actuator 221 and accompanying raising movement of the implement 215. As the piston 15 223 moves, it forces fluid from the cylinder 222 through theconduits 227 and 132 to the actuator 68. This movm the lift shaft 76 and the arm 74, causing the follow up mechanism to return the valve plunger 82 to neutral to prevent further movement of the implement.

To lower the implement 215 the position control lever 61 is moved forwardly to effect movement of the plunger 82 to its discharge position. The weight of the implement causes movement of the piston 223 and forces fluid through the conduit 226 back to the conduit 132 and the reservoir. At the same time, a tension spring 231 connected to the lift arm 77 and the bracket 21 on the tractor is effective to force fluid out of the actuator 68 and through the conduits 132 and 227 to the rod end of the cylinder 222. As fluid is exhausted from the actuator 63, swinging movement of the lift arm 77 and arm 74-actuate the follow up linkage to return the valve to its neutral position and prevent further implement lowermg.

From this it will be seen that pulled implements may be controlled in the same manner as mounted implem'ents. Draft control is accomplished by pulling the implement from the control frame 22 and by supplying fluid directly to one end of an auxiliary cylinder associated with the pulled implement. Position control is obtained by providing a closed circuit between the other end of the auxiliary actuator 221 and the actuator 68 and by adding a spring or the like to force fluid from the actuator 68 when the implement 215 is lowered.

Auxiliary equipment In addition to hitching and controlling both mounted and pulled implements, it is sometimes necessary to operate the tractor with auxiliary hydraulic equipment. For example, tractor mounted loaders and cranes may employ one or more hydraulic cylinders. In such cases, it becomes necessary to provide a source of pressure fluid for the cylinders. In the present instance, the same hydraulic system which supplies the actuator 68 in the case of mounted implements or the auxiliary actuator 221 in the case of pulled implements is used to establish a source of pressure fluid for the auxiliary equipment. Such operation can be understood best from an examination of FIG. 8, in which the position controlling lever 61 is normally movable in a range between positions A and B. When the lever is at position A, the draft links 19 will be at their lowermost position and rearward movement of the lever 61 will eflect a raising of the linkage. When the lever 61 reaches position B it engages a stop plate 236 attached to the quadrant 237, which acts as a guide for the lever. In this position of the lever the implement will be fully raised and the piston rod 73 will have moved arm 74 until it abuts a stop formed by the rear end of the housing cover 71. If the lever is maintained at position B, the follow up mechanism including the lever 143 and link 124- will be effective to return the valve plunger 82 to neutral as previously described. However, if the lever 61 is deflected away from the quadrant 237, it may be moved rearwardly past the stop 236 into a second range of lever movement between positions B and the full line position indicated at C. Such movement swings the position control cam lever 121 clockwise, moves links 127 downwardly and swings rocker arm 113 counterclockwise, so that the valve plunger 82 is moved to an intake positon. Ordinarily, this would cause fluid flow and rearward movement of the piston 72. However, the arm '74 is prevented from moving and the follow up mechanism including the lever 143 and the link 124 is not effective to return the valve plunger to neutral to prevent fluid flow. Consequently, the plunger 82 is maintained in its supply of pump intake position and the pump continues to deliver fluid to the fully extended actuator 68. Under such conditions fluid may be bled from the conduit 132 to supply auxiliary mechanism requiring pressure fluid. Pressure fluid may be bled from the conduit 132 by removing the transfer plate 230 shown in FIGS. 2 and 8 and by substituting another plate affording a branch passage to which an external conduit or valve may be connected externally of the tractor housing. Consequently, an implement such as a loader mounted on the tractor may be raised and lowered by means of an auxiliary hydraulic cylinder which receives fluid from the branch passage in the transfer plate and exhaust fluid from the auxiliary cylinder to the reservoir. Even in such instances, the damping mechanism 189 performs an important function. For example, with a loader in its raised position, deliberate or actual movement of the position control lever 61 permits exhaust of fluid from the auxilialy mechanism. The loader is, consequently, prevented from dropping at an excessive rate since movement of the valve plunger initiated by movement of the lever 61 is retarded and the implement drops slowly and safely.

As seen in FIG. 3, a shutoff valve 233 may be located in the conduit 132 between the transfer plate 230 and the actuator 68. This valve is provided with an external control knob 234 which, as shown in FIGS. 2 and 8, may be manipulated to block the flow of fluid to and from the actuator. Consequently, when the valve 233 is closed pressure fluid may flow in the conduit 132 and through the transfer plate 230 without affecting the position of the actuator 68 or an implement mounted on the draft links 19.

Rsum of operation The described implement hitch and control system is capable of operating a great many types of implements and its utility becomes particularly apparent when considering some typical operations of the viewpoint of the farmer.

To prepare for plowing, the tractor is backed up to the plow, the hitch links 18 and 19 are attached and the lever 61 is moved rearwardly to the position shown at B in FIG. 8. This raises the implement from the ground to its fully raised position so that it may be transported to the field. At the field the operator moves the lever 62 to a forward position and then moves the lever 61 beyond that position. The implement will drop to and enter the ground until the load on the implement increases and moves the frame 22 against the action of the spring 53. When the spring 53 balances the load on the implement, the valve plunger 82 blocks further flow of fluid and lowering movement of the plow stops. If the plow is not at its proper depth the operator can move the lever 62 rearwardly or forwardly a slight amount to position the implement at the desired depth. The operator may want to make other adjustments. For example, if the implement dropped too rapidly he may adjust the position of the cam 176 by swinging the lever 178 in FIG. 2 rearwardly to limit the distance that the valve plunger 82 can move in the discharge direction. This limits the maximum rate at which fluid can be discharged and, consequently, controls the rate at which the implement will drop. If movement of the implement from its transport position to the ground was erratic or if the soil subjects the plow to rapidly fluctuating loads, the operator may shift the lever 209 in FIG. 7 to restrict the flow of oil from the passage 198 to the passage 197. This is effective to control the rate of movement of the valve plunger 82. Consequently, an instantaneous reduction in the load on the control frame 22 is ineffective to bring about a change in implement elevation. In the case of an implement in the ground, the plunger movement is retarded and the implement load returns to normal before the unnecessary correction can occur.

With the necessary adjustments made, the operator pulls the position control lever 61 rearwardly to raise the plow at the end of the field. When he is ready to return the implement to the ground he moves the lever 61 forwardly and the implement enters the ground subject to the adjustments which were made previously.

attachment to another implement.

In the event that the ground .to be plowed .is uneven or if the soil causes periodic tire deflection and'permits the tires to sink, the angle of attack of the implement may change. In order to prevent this from occurring, the operator may change the location of the virtual hitch point determined by the convergence of the upper link 18 and the lower links 19. By adjusting the forward end of the link 18 upwardly on the bracket 22 the virtual hitch point is moved forwardly so that tire deflection and sinking of the rear wheels in the ground does not affect the attitude or angle of the implement. By downward adjustment, the virtual hitch point is moved rearwardly and vertical movement of the front wheels over uneven terrain will not seriously affect implement depth orchange the implement angle.

After the plowing operation, the tractor operator can transport the plow to its place of storage, drop it to the ground and detach the links 18 and 19 in readiness for If the new implement is of a different size, its attaching points for receiving the links 18 and 19 may be at a different vertical spacing. This affects the convergence of the upper and lower link means and the location of the virtual hitch point. If the virtual hitch point appears to be in an undesirable location the operator merely adjusts the link.

18 relative to the bracket 21 In some cases it may be necessary to change from a mounted implement to a pulled implement such as shown in FIG. 10. The necessary changes are accomplished by connecting the implement to the control frame 22, connecting conduits 226 and 227 from the auxiliary cylinder 221' to the conduit 132, closing valve 228 and adding a spring 231 from the lift arm 77 to the bracket 21. With this modification, the driver may operate the implement and make the various adjustments to the hydraulie system in the same manner as he did in the case of mounted implements.

If the operator should decide to use some other type of implement such as a loader or a crane which requires pressure fluid, he merely moves the position control lever '61 rearwardly to the position shown at C in FIG. 8 and pressure fluid is made available in the conduit 132. Fluid may be bled from this conduit to supply the auxiliary hydraulic equipment.

It is not intended to limit the invention to the above described forms and details, and the invention includes other forms and modifications embraced by the scope of the appended claims.

I claim as my invention:

1. In a tractor having a fluid operated actuator for raising and lowering an implement connected to' said tractor, the combination of, a reservoir containing fluid,

valve means disposed in said reservoir and controlling the flow of fluid between said actuator and said reservoir, said valve means being shiftable to a supply position for raising said implement and to an exhaust position for lowering said implement, a cylinder element disposedin said reservoir, a piston elementdis posed in said cylinder for movement in one direction to force fluid from said cylinder and in the other direction to permit fluid flow into said cylinder, one-way connecting means between said valve means and said piston for moving said piston in said one direction upon movement of said valve means to said exhaust position and permitting movement of said valve means to said supply position independently of said piston, first resilient means associated with said valve means for moving the latter together with said piston in said exhaust direction, and second resilient means associated with said piston for moving the latter in said other direction upon movement of said valve means toward said supply position.

2. In a tractor having a fluid operated actuator for raising and lowering an implement connected to said tractor, the combination of, a reservoir containing fluid, valve means disposed in said reservoir for controlling the flow of .fluid .between said actuator and said reservoir,

said valve means being shiftable in opposite directions from a neutral position to a supply position for raising said implement and to an exhaust position for lowering said implement, a cylinder element immersed in the fluid in said reservoir, a piston element slidable in one direction in said cylinder to force fluid therefrom and slidable in the other direction to permit flow of fluid into said cylinder, one-way connecting means between said valve means and said piston whereby said piston retards movement of said valve means from said neutral to said discharge position and permits independent movement from said exhaust position to said supply position, first resilient means associated with said valve means for moving the latter from said supply position to said exhaust position, and second resilient means associated with said piston for moving the latter in said other direction upon movement of Said valve means from said exhaust position to said neutral position.

3. In a tractor hydraulic system including control means movable to actuate said system, an elongated control frame, a bracket connected to the underside of said tractor and slidably supporting a forward end of said frame in vertically fixed relation on said tractor, a pair of links pivoted to said tractor and to opposite sides of a rear part of said frame for swingably supporting a rear portion of said frame, a spring, spring seats connected to said frame and engaging opposite ends of said spring, a support connected to said tractor, said spring reacting between said bracket and one of said spring seats upon forward movement of said frame and between the other of said spring seats and said support upon rearward movement of said frame, and means connecting said frame to said control means for moving the latter upon movement of said frame. l

4. In a control mechanism for actuating a hydraulic system of a tractor in response to loads imposed on an implement connected to said tractor, said mechanism inveluding an elongated frame for supporting said imple- .one of said seat members and said bracket upon forward movement of said frame and havingits opposite ends engaging the other of said seat members and said support member upon rearward movement of said frame.

5. Inv a tractor hydraulic system including control means movable to actuate said system, an elongated control frame, a bracket connected to the underside of said tractor and slidably supporting a front of said frame in pivoted to opposite sides of said tractor and to opposite sides of a rear portion of said frame, a support rigidly mounted on said tractor in longitudinally spaced relation to said bracket, 2. pair of guide elements mounted on said bracket and said support, respectively, and engaging said frame to guide the latter in a longitudinal path, said frame including a pair of longitudinally aligned seat elements, a spring having opposite ends engaging one of said seat elements and said bracket upon forward movement of said frame and engaging said support and the other of said plungers upon rearward movement of said frame, and means connecting said control means and said frame for moving said control means in response to movement of said frame.

6. For use in connecting a ground working implement to a tractor having a hydraulic control system, the cornbination of, a control frame disposed adjacent the lower side of said tractor for movement longitudinally thereof, upper and lower link means adapted for connection to vertically spaced points on said implement and being pivotally connected to said tractor and said name, re spectiv'ely, said link means converging forwardly to afford a virtual hitch point for said implement, said virtual hitch point being movable upon swinging movement of said link means, a hydraulic actuator connected to said link means for swinging the latter, valve means ienov'able to control the supply of pressure fluid to and the exhaust of fluid from said actuator to effect, respectively, raising and lowering of said link means, means connecting said control frame and said valve means for initiating movement of the latter upon movement of said frame, and adjustable damping means connected to 'said valve means and operable to retard the movement of said valve means in an exhaust direction to select the rate of upward movement of said virtual hitch point.

7. In a tractor having a hydraulic control system, a control frame disposed adjacent a lower side of said tractor for fore and aft movement, lower implement link means connected to said control frame for vertical swinging movement and for bodily movement with said frame, a hydraulic actuator operatively associated with said lower link means for raising and lowering the latter, valve means movable to control the supply of fluid to and the exhaust of fluid from said actuator to effect said link means and the location of said virtual hitch point forwardly of said frame.

8. In an implement hitch and control mechanism for a tractor including hydraulically actuated lift arms and valve means movable to control the movement of said lift arms, the combination of upper and lower link means adapted for detachable connection with vertically spaced portions on an implement, a control fr'ame pivotally supporting said lower link means and being mounted adjacent the lower side of said tractor for fore and aft movement, means connecting said frame to said valve means for moving the latter in response to movement of said frame, hitch means including vertically spaced hitch points mounted in fixed relation on said tractor and disposed above said control frame, said upper link means being detach'ably connected to a selected one of said hitch points spaced from said frame a distance less than the distance between said vertically spaced portions on said implement to selectively determine a point of convergence of said link means forwardly relative to said movable control frame.

9. In a hitch and control system for connecting an implement to a tractor having a power actuated lift mechanism including a valve element movable to actuate said lift mechanism, a control frame disposed at the underside of said tractor for horizontal fore and aft movement, means connected to said frame and said valve element for moving the latter in response to movement of said frame, a bracket fixed to said tractor above said frame and forming a plurality of generally vertically disposed hitch points, upper and lower link means having rear portions pivotally connected to vertically spaced portions on said implement, said lower link means being pivotally connected to said frame for vertical swinging movement and for movement therewith, said upper link means converging relative to said lower link means and being detachably connected to a selected one of said hitch points for determining a point of convergence, and a. vertically disposed lift link connected at its upper end to said lift mechanism and at its lower end to said lower link means for swinging the latter vertically relative to said frame upon movement of said lower link means with said frame in response to draft loads on said implement.

10. In a tractor having a hydraulic control system, a control frame disposed adjacent the underside of said tractor for fore and aft movement in a horizontal path, a pair of implement hitch links connected in laterally spaced relation on said control frame for universal swinging movement and for bodily movement with said frame, a hydraulic actuator operatively associated with said pair of hitch links for raising and lowering the latter, valve means movable to control the supply of fluid to and the exhaust of fluid from said actuator to effect a raising and lowering of an implement connected to said pair of links, means for moving said valve means in response to movement of said frame, an upper link adapted for connection to said implement and converging forwardly relative to said pair of lower links to afford a virtual hitch point for said implement, a bracket member having a plurality of vertically spaced hitch points fixed on said tractor above the path of movement of said frame, said upper link being pivotally connected to a selected one of said hitch points to determine the degree of convergence of said upper link with said pair of links for determining the location of the virtual hitch point forwardly relative to said control frame.

11. In a tractor having a power actuated system, the combination of, an arm swingable on the tractor, stop means on said tractor engageable with said arm to limit swinging movement of the latter in on direction, a hydraulic actuator connected to said arm for swinging the latter toward and away from said stop means upon supply of fluid to and exhaust of fluid from said actuator, respectively, valve means having a neutral position effective to block delivery of fluid to and exhaust of fluid from said actuator, said valve means being shiftable from said neutral position to a supply position for initiating delivery of pressure fluid to said actuator to cause swinging of said arm toward said stop means and being shiftable from said neutral position to an exhaust position to permit flow of fluid from said actuator to cause swinging of said arm away from said stop means, a control lever pivotally mounted on said tractor, control means including a linkage operatively connected with said valve and operable jointly in accordance with the positions of said control lever and said arm to shift said valve for effecting movement of the arm to a position corresponding to that of the lever, said lever being swingable in a first direction from a predetermined position in which said arm is engaged with said stop means to move said valve means to and maintain it at said supply position and movable in a second direction from said predetermined position to move said valve to said exhaust position to cause swinging of said arm away from said stop means, and adjustable damping means associated with said valve for retarding the rate of movement of the latter to said exhaust position.

12. In a tractor having an implement hitch movable to selected positions between fully raised and lowered positions on said tractor, the combination comprising, a hydraulic actuator connected to said hitch for raising and lowering the latter, valve means having a neutral position effective to block the flow of fluid to and from said actuator and being shiftable in one direction to initiate delivery of fluid to said actuator to cause raising of said hitch and being progressively shiftable in the other direction to vary the exhaust of fluid from said actuator between minimum and maximum rates, a lever pivoted on said tractor, control means including a linkage operatively connected with said valve and operable jointly in accordance with the positions of said lever and said hitch to position said valve to move the hitch to an elevation corresponding to the positio of said lever, said lever being swingable in a first direction from a predetermined location corresponding to a fully raised position of said bitch to move said valve in said one direction, adjustable damping means associated with said valve means to retard the rate of movement of said valve means in said one direction, said lever being swingable in a second direction from said predetermined location independently of said damping means to shift said valve in said other direction and to maintain it in its shifted position whereby said hitch is elevated to a fully raised position and a constant source of pressure fluid is available at said actuator.

13. 'In a control system for a tractor adapted for use with implements of widely differing weights and operating characteristics and having a hydraulic actuator connected for raising and lowering the implement coupled to the tractor, in combination, a source of pressure fluid, valve means connected with the actuator and said pressure fluid source including a valve member having a neutral position in which it is effective to block both the delivery of pressure fluid to and exhaust of fluid from the actuator, said valve member being movable in one direction from said neutral position to initiate the delivery of pressure fluid from said source to the actuator to raise the implement and being movable in the opposite direction from the neutral position to initiate the exhaust of fluid from the actuator with consequent lowering of the implement, the exhaust rate from the actuator increasing progressively as the valve member moves from the neutral position, spring means biasing said valve member toward the implement lowering position, control means including an element variably positioned in accordance with the draft load imposed on the tractor by the implement, a linkage connecting said element with said valve member operative to retain the valve member in neutral position and to shift it toward raising or lowering position to maintain said draft force substantially constant, said linkage including a one-way connection whereby the valve member is moved positively in a raising direction and released for movement by said spring means in a lowering direction, damping means acting on said valve member to control its rate of movement in said lowering direction, and means for adjusting said damping means to selectively set the maximum rate of movement of the valve member at a value effective to prevent overcontrol of the actuator by the particular implement coupled to the tractor.

14. In a control system for a tractor adapted for use with implements of widely differing weights and operating characteristics and having a hydraulic actuator connected for raising and lowering the implement coupled to the tractor, in combination, a source of pressure fluid, valve means connected with the actuator and said pres sure fluid source including a valve member having a neutral position in which it is effective to block both the delivery of pressure fluid to and exhaust of fluid from the actuator, said valve member being movable in one direction from said neutral position to initiate the delivery of pressure fluid from said source to the actuator to raise the implement and being movable in the opposite direction from the neutral position to initiate the exhaust of fluid from the actuator with consequent lowering of the implement, the exhaust rate from the actuator increasing progressively as the valve member moves from the new tral position, spring means biasing said valve member toward the implement lowering position, control means operative to shift the valve member in an implement raising direction and to release the member for movement by said spring means in an implement lowering direction, means connected with said valve member operative to restrict its rate of movement by said spring means while permitting substantially unrestricted movement of the valve by said control means, and means for adjusting said restricting means to limit the maximum rate of movement of said valve member to a value effective to insure smooth descent of the implement coupled to the tractor irrespective of the downwardly directed forces acting on the implement.

15. In a tractor, in combination, means providing a draft connection with a ground working implement including a frame, a bracket depending from the underside of the tractor slidably supporting the forward end of said frame, a support member depending from the tractor rearwardly of said bracket, a pair of links pivoted to the tractor and the rear portion of the frame supporting the frame for fore-and-aft movement relative to the tractor, spring seats carried by said frame, a compression spring interposed between said seats, one of said seats being positioned to engage said bracket upon movement of the frame in one direction and the other of said seats being positioned to engage said support member upon movement of the frame in the opposite direction whereby to impose the force of said spring against the movement of the frame, a hydraulic actuator connected to and operative to raise and lower the implement connected to said frame, a source of pressure fluid on the tractor, valve means controlling the flow of pressure fluid from said source to and the exhaust of pressure fluid from said actuator, and a linkage connected between said frame and said valve means for operating the valve means in response to movements of said frame.

16. In a tractor, in combination, means providing a draft connection with a ground working implement including a frame, a bracket depending from the underside of the tractor slidably supporting the forward end of said frame, a support member depending from the tractor rearwardly of said bracket, a pair of links pivoted to the tractor and the rear portion of the frame supporting the frame for fore-and-aft movement relative to the tractor, spring seats carried by said frame, a compression spring interposed between said seats, one of said seats being positioned to engage said bracket upon movement of the frame in one direction and the other of said seats being positioned to engage said support member upon movement of the frame in the opposite direction whereby to impose the force of said spring against the movement of the frame, a hydraulic actuator mounted on the implement coupled to the frame operative to raise and lower the ground working element of the implement, a source of pressure fluid on the tractor, valve means on the tractor, fluid connections between said fluid source, said valve means and said actuator, said valve means being operative to control the delivery of pressure fluid to and exhaust of pressure fluid from said actuator to effect the raising or lowering of the implement, and a linkage connected between said frame and said valve means for operating the valve means in response to movements of the frame.

References Cited in the file of this patent UNITED STATES PATENTS 1,712,089 Miles May 7, 1929 2,118,181 Ferguson May 24, 1938 2,179,788 Hinton et al Nov. 14, 1939 2,395,671 Kleinhans et al. Feb. 26, 1946 2,437,875 Chambers et a1 Mar. 16, 1948 2,495,785 Stephens Jan. 31, 1950 2,679,199 Strehlow May 25, 1954 2,695,153 Gillaspy Nov. 23, 1954 2,714,346 Valin Aug. 2, 1955 2,730,029 Brundage Jan. 10, 1956 2,734,290 Tuttle Feb. 14, 1956 FOREIGN PATENTS 1,139,224 France Feb. 11, 1957 576,684 Great Britain Feb. 1, 1946

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